Classification of Nerve Injuries & their prognosis

By Seddon(1943) into 3 groups:

1. Neuropraxia– →Physiological disruption of impulse transmission,
   →Minor contusion/compression of a peripheral nerve; preserved axis cylinder ; minor oedema or breakdown of myelin sheath locally.
   →Recovery is complete in a few days/weeks.
2. Axonomesis– →Injury to axon; distal wallerian degeneration; Preservation Schwann cell & Endoneurial tubes
   →Spontaneous regeneration with good functional recovery.
3. Neurotmesis– →The complete anatomical severance of nerve &/or extensive avulsion or crushing
   →The axon, Schwan cell & endoneurial tube- completely disrupted
   →Perineurium & Epineurium- varying degree of injury & disruption
   →Usually no expectation of spontaneous recovery.

By Sunderland (1951) into 5 degrees: more clinical application- with each degree of injury, more anatomical disruption & decreasing prognosis.

1. 1^st degree injury (I): →Physiological disruption of impulse conduction along the axon; No anatomical disruption, & no wallerian degeneration.
   →Injury similar to Neuropraxia of Seddon
   →Motor > Sensory (Proprioception, touch, temperature, & pain in that order)
   →Proprioception & Motor- last to return.
   →Simultaneous return of motor function in the proximal & distal muscles – No “Motor-march”
   →No Tinel sign, as no axonal damage or regeneration.
   →Recovery- spontaneous & complete in days to weeks.
2. 2^nd degree injury (II):  →Disruption of axon & wallerian degeneration distal to the injury & proximal degeneration upto one/more nodes.
   →Endoneurial tube maintained- a perfect anatomical course for regeneration
   →Complete neurological deficit (Motor, Sensory & Autonomic)
   →Motor reinnervation in a progressive manner- from proximal to distal- “Motor march”.
   →Advancing Tinel sign at a rate of 1 inch/month
   →Good functional return.
3. 3^rd degree injury (III) : →Both the axons & endoneurium- disrupted; Perineurium preserved.
   →Complete neurological deficit
   →Motor-march from proximal to distal & an advancing Tinel sign +nt.
   →No complete recovery of neural function as against 2^nd degree injury & more time needed for the recovery.
4. 4^th degree injury (IV) : →Disruption of the axon & endoneurium,; some of the endoneurium & some of the perineurium intact—– no complete severance of the entire nerve trunk.
   →Retrograde degeneration more severe
   →Nerve continuity maintained by scar tissue- prevents proximal axons from entering the distal endoneurial tubes; axonal sprouts exit through defects & wander in surrounding tissues.
   →Prognosis of functional recovery is poor, & needs surgery.
5. 5^th degree injury (V) : → complete transection of the nerve with variable distance between neural stumps.
   →Injury only in open wounds & can be identified at early surgical exploration
   →Prognosis is poor & need surgery.
   →Appropriate surgery needed to gain any significant functional return.

6^th degree injury (VI):  (by Mackinnon) – Mixed injuries→ the nerve trunk is partially severed & the remaining part has 4^th degree, 3^rd degree, 2^nd degree or even 1^st degree injury.
→A neuroma-in-continuity +nt.
→The recovery pattern is mixed
→If surgery is done to correct 4^th & 5^th degree components, can cause loss of function of lesser degree injured fascicles.